The related applications relate to a power supply controller which can be used for controlling a plurality of isolating power supplies, such as switch mode power supplies or DC power converters, for providing controlled electrical power to loads. For example, the power supplies may provide different supply voltages to various electrical circuits on a circuit card on which the power supply controller is also provided.
In such a power supply controller, separate IC (integrated circuit) control units can be provided on the primary and secondary sides of a transformer that serves to maintain an electrical isolation barrier between input and output sides of the isolating power supplies. The transformer conveniently provides for signal coupling in both directions between the primary and secondary control units, and also for power transfer from its primary to its secondary side to supply operating power to the secondary control unit and any related circuits (for example, a non-volatile memory) of the power supply controller on the secondary side of the transformer.
As described in the related applications, the power supply controller and the signal coupling within it are arranged for controlling up to six power supplies. To this end, each of the primary and secondary control units has six converter state machines (CSMs), one for each of up to six controlled power supplies, as well as an input state machine (ISM) relating to an input or supply voltage.
The power supplies are sequenced, i.e. enabled in a predetermined sequence, and disabled in a predetermined, typically reverse, sequence, in accordance with conditions monitored by the power supply controller. The monitored conditions include, for example, output voltages produced by the respective power supplies, and an input voltage of a power source which powers all of the power supplies and the power supply controller. Thus, for example, enabling of each power supply on power-up of the circuit card can be dependent upon the input voltage, or upon a monitored output voltage of a prior-enabled power supply, exceeding a threshold voltage.
The related application by D. Brown et al. discloses arrangements of power supplies that can provide relatively arbitrary sequence topologies. However, there remains a potential problem where the power supply controller is provided on a main circuit card, referred to herein as a mother board, and one or more of the controlled power supplies is provided on a subsidiary circuit card, typically mounted on the mother board and referred to herein as a daughter board. In such a situation it may be desirable, especially for testing purposes, to operate circuits on the mother board without the daughter board being present, but the consequent absence of the power supplies on the daughter board means that the power supply controller will not detect monitored output voltages of such power supplies exceeding the respective thresholds.
Accordingly, there is a need to avoid this potential problem in sequencing one or more power supplies which may be provided on a daughter board.